The potassium bromate, which is a bromate, has been known as a compound having carcinogenic potential for humans. On the other hand, in water purification plants and the like, advanced water treatment employing ozonation and the like has been performed. However, when the water containing bromide ion (Br−) such as river water is treated with oxidation such as ozonation and the like, bromate ion (BrO3−) is produced as a reaction by-product. Thus, in recent years, with respect to the concentration of bromate ions contained in water such as tap water and the like, reference values have been defined in the water quality standard and the like, and the bromate ion concentration in the water has been measured.
Here, in Japan and the like, as a measuring method of bromate ion concentration in the water, the ion chromatograph-post column method (IC-PC method) has been used as an official method. However, in the IC-PC method, bromate ions separated from a water sample using an anion-exchange column react with bromide ions (Br−) under acid condition to convert the bromate ions into tribromide ions (Br3−), and after that, the ultraviolet absorbance of the produced tribromide ions is measured, thereby the quantity of bromate ions is determined. Therefore, the IC-PC method had a problem of complicated operation and being unsuitable for a continuous measurement of bromate ion concentration.
Therefore, in recent years, as a method by which the bromate ion concentration in the water can be measured with a simple operation, a quantitative method has been proposed in which a fluorescent substance such as trifluoperazine (TFP) whose fluorescence intensity changes in response to the bromate ion concentration is used. More specifically, in Patent Literature 1, for example, a method has been proposed in which, first, bromate ions in a water sample is selectively adsorbed to an anion-exchange column, then a hydrochloric acid solution containing TFP as a fluorescent substance is passed through the anion-exchange column to elute bromate ions into the hydrochloric acid solution, after that, the fluorescence intensity of the hydrochloric acid solution containing the bromate ions eluted is measured, and finally, the measured value of the fluorescence intensity is compared with the previously prepared calibration curve, thereby the bromate ion concentration in the water sample is calculated. According to the measuring method described in this Patent Literature 1, a measurement is made after the bromate ions are selectively adsorbed to the anion-exchange column, and as a result of this, a measured value of the fluorescence intensity can be prevented from being influenced by interfering substances such as iodate ions and the like coexisting in the water sample. Therefore, according to the measuring method described in Patent Literature 1, the bromate ion concentration can be measured accurately. Furthermore, according to the measuring method described in Patent Literature 1, it is not necessary to convert the bromate ions desorbed from the anion-exchange column into tribromide ions (Br3−) as is in the case of the IC-PC method, thus the bromate ion concentration in the water can be measured with a simple operation.